Micro pump

ABSTRACT

A micro pump includes: a vibrating membrane on which a piezoelectric element is stacked; an upper space provided in contact with an upper surface of the vibrating membrane; and a lower space provided in contact with a lower surface of the vibrating membrane, wherein by displacing the vibrating membrane toward the upper space, a fluid flows out from the upper space to an outside and flows in from the outside to the lower space, and wherein by displacing the vibrating membrane toward the lower space, the fluid flows out from the lower space to the outside and flows in from the outside to the upper space.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-097253, filed on Jun. 16, 2022, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a micro pump.

BACKGROUND

MEMS (Micro Electro Mechanical Systems) type micro pumps that utilize piezoelectric thin film technology are known in the related art. For example, there is a known micro pump using a piezoelectric element.

However, since conventional micro pumps are small, there is a problem that it is difficult to increase a flow rate.

SUMMARY

Some embodiments of the present disclosure provide a micro pump capable of increasing a flow rate even when the micro pump is small in size.

According to one embodiment of the present disclosure, a micro pump includes: a vibrating membrane on which a piezoelectric element is stacked; an upper space provided in contact with an upper surface of the vibrating membrane; and a lower space provided in contact with a lower surface of the vibrating membrane, wherein by displacing the vibrating membrane toward the upper space, a fluid flows out from the upper space to an outside and flows in from the outside to the lower space, and wherein by displacing the vibrating membrane toward the lower space, the fluid flows out from the lower space to the outside and flows in from the outside to the upper space.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure.

FIG. 1 is a cross-sectional view of a boundary between an upper member and a lower member of a micro pump according to a first embodiment.

FIG. 2 is a cross-sectional view of the micro pump according to the first embodiment, taken along line A-A in FIG. 1 .

FIG. 3 is a plan view showing a structure of the upper member of the micro pump according to the first embodiment, and is a view seen from below.

FIG. 4 is a plan view showing a structure of the lower member of the micro pump according to the first embodiment, and is a view seen from below.

FIG. 5 is a view for explaining an operation of the micro pump according to the first embodiment.

FIG. 6 is a view for explaining an operation of the micro pump according to the first embodiment.

FIG. 7 is a plan view showing a structure of an upper member of a micro pump according to a second embodiment, and is a view seen from below.

FIG. 8 is a plan view showing a structure of a lower member of the micro pump according to the second embodiment, and is a view seen from below.

FIG. 9 is a plan view showing a structure of a lower member of a modification of the micro pump according to the second embodiment, viewed from below.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments.

First Embodiment

A first embodiment of the present disclosure will be described below with reference to the drawings. Throughout the drawings, the same parts are denoted by the same reference numerals, and detailed explanation thereof will be omitted. However, it should be noted that the drawings are schematic and a relationship between a thickness of each component and a planar dimension thereof, etc. is different from an actual one. Therefore, specific thicknesses and dimensions should be determined with reference to the following description.

Structure of Micro Pump

A structure of a micro pump 1 according to a first embodiment will be described with reference to FIGS. 1 and 2 . FIG. 1 is a cross-sectional view of a boundary (line B-B in FIG. 2 ) between an upper member and a lower member of the micro pump 1 according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1 . As shown in FIGS. 1 and 2 , the micro pump 1 according to this embodiment is mainly composed of an upper member 3, a lower member 5, and a bottom plate 7. A vibrating membrane 9 is formed in the lower member 5 and a piezoelectric element 11 is stacked on an upper surface of the vibrating membrane 9. In the following description, a vertical direction is defined based on a state of the micro pump 1 shown in FIG. 1 , but a direction in which the micro pump 1 is used is not limited.

The upper member 3 is made of a (semiconductor) material such as silicon (Si), and a cylindrical upper space 31 is formed in a central portion by etching or the like. FIG. 3 is a plan view showing a structure of the upper member 3, and is a view seen from below. As shown in FIG. 3 , the upper member 3 has a quadrangular shape when viewed from a film thickness direction of the vibrating membrane 9, and the upper space 31, an upper inflow path 33, and an upper outflow path 35 are formed by selectively etching a lower surface side of the upper member 3. In addition, a notch 40 for exposing an electrode pad, which will be described later, is provided in the upper member 3.

The upper space 31 is a cylindrical space provided in contact with the upper surface of the vibrating membrane 9 formed in the lower member 5, and has a circular shape when viewed from the film thickness direction of the vibrating membrane 9. Thus, a vertical movement of the vibrating membrane 9 causes a fluid to flow in from the upper inflow path 33 to the upper space 31 and flow out to the upper outflow path 35.

The upper inflow path 33 connects an upper inflow port 37, which is provided on a side surface of the upper space 31, to the outside, and the fluid flows into the upper space 31 from the outside via the upper inflow path 33. Since a shape of the upper inflow path 33 when viewed from the film thickness direction of the vibrating membrane 9 is such that a width of the upper inflow path 33 gradually widens from the outside toward the upper inflow port 37, the fluid can be prevented from flowing back from the upper space 31 to the outside without providing a check valve.

The upper outflow path 35 connects an upper outflow port 39, which is provided on a side surface of the upper space 31, to the outside, and the fluid flows from the upper space 31 to the outside via the upper outflow path 35. Since a shape of the upper outflow path 35 when viewed from the film thickness direction of the vibrating membrane 9 is such that a width of the upper outflow path 35 gradually widens from the upper outflow port 39 toward the outside, the fluid can be prevented from flowing back from the outside to the upper space 31 without providing a check valve.

The lower member 5 is made of a (semiconductor) material such as silicon (Si), and by selectively etching a lower surface side of the lower member 5, the circular vibrating membrane 9 and a cylindrical lower space 51 are formed in a central portion. FIG. 4 is a plan view showing a structure of the lower member 5, and is a view seen from below. As shown in FIG. 4 , the lower member 5 has a quadrangular shape when viewed from the film thickness direction of the vibrating membrane 9, and the lower space 51, a lower inflow path 53, and a lower outflow path 55 are formed by selectively etching a lower surface side of the lower member 5. In addition, electrode pads 60 for applying a drive voltage to the piezoelectric element 11 are provided on a side of an upper surface of the lower member 5. Two electrode pads 60 are connected to upper and lower electrodes of the piezoelectric element 11, respectively.

The vibrating membrane 9 is composed of a thin film connected to an inner peripheral surface of the lower space 51 so as to block an upper surface of the lower space 51. The piezoelectric element 11 is stacked on the upper surface of the vibrating membrane 9, and when the piezoelectric element 11 is deformed, the vibrating membrane 9 is displaced in the film thickness direction, that is, in the normal direction of the vibrating membrane 9.

The piezoelectric element 11 has a structure in which electrodes are stacked on upper and lower surfaces of a piezoelectric film, respectively. By applying drive voltages to the upper and lower electrodes, respectively, the piezoelectric element 11 is deformed to displace the vibrating membrane 9 vertically. In addition, by repeatedly applying the driving voltages to the piezoelectric element 11, the vibrating membrane 9 alternately repeats upward displacement and downward displacement. Such vibration of the vibrating membrane 9 causes the micro pump 1 to flow the fluid in and out with respect to the outside. A planar shape of the piezoelectric element 11 corresponds to a planar shape of the vibrating membrane 9, and thus has a circular shape.

The lower space 51 is a cylindrical space provided in contact with a lower surface of the vibrating membrane 9, and has a circular shape when viewed from the film thickness direction of the vibrating membrane 9. The vertical movement of the vibrating membrane 9 causes the fluid to flow in from the lower inflow path 53 to the lower space 51 and flow out to the lower outflow path 55. In FIG. 4 , an outer periphery of the upper space 31 is indicated by a dotted line. As shown in FIG. 4 , a diameter of the lower space 51 is smaller than a diameter of the upper space 31. Thus, since an outer periphery of the vibrating membrane 9 is disposed inside an inner peripheral surface of the upper space 31, influence of the vibration of the vibrating membrane 9 on the upper member 3 can be reduced, thereby improving durability.

The lower inflow path 53 connects a lower inflow port 57, which is provided on a side surface of the lower space 51, to the outside, and the fluid flows from the outside into the lower space 51 via the lower inflow path 53. Since a shape of the lower inflow path 53 when viewed from the film thickness direction of the vibrating membrane 9 is such that a width of the lower inflow path 53 gradually widens from the outside toward the lower inflow port 57, the fluid can be prevented from flowing back from the lower space 51 to the outside without providing a check valve.

The lower outflow path 55 connects a lower outflow port 59, which is provided on a side surface of the lower space 51, to the outside, and the fluid flows from the lower space 51 to the outside via the lower outflow path 55. Since a shape of the lower outflow path 55 when viewed from the film thickness direction of the vibrating membrane 9 is such that a width of the lower outflow path 55 gradually widens from the lower outflow port 59 toward the outside, the fluid can be prevented from flowing back from the outside to the lower space 51 without providing a check valve. In addition, as shown in FIG. 4 , an opening 65 is provided at a position where the upper outflow path 35 and the lower outflow path 55 overlap in the thickness direction of the vibrating membrane 9. Thus, the upper outflow path 35 and the lower outflow path 55 merge into a single path.

The bottom plate 7 has a quadrangular shape when viewed from the film thickness direction of the vibrating membrane 9, and is disposed below the lower member 5. The bottom plate 7 is coupled with the lower member 5 to seal the lower space 51.

The micro pump 1 according to the present embodiment is constructed integrally as shown in FIGS. 1 and 2 by stacking and coupling the upper member 3, the lower member 5, and the bottom plate 7 described above. The structure of the spaces and flow paths formed inside the micro pump 1 will be described with reference to FIG. 1 .

As shown in FIG. 1 , the upper inflow port 37 and the lower inflow port 57 are provided on the side surfaces of the upper member 3 and the lower member 5 in the same direction, that is, the side surfaces on the left-hand side, respectively. However, since the upper inflow port 37 and the lower inflow port 57 deviate from each other in a lateral direction, the upper inflow port 37 and the lower inflow port 57 are disposed at positions where they do not overlap with each other in the film thickness direction of the vibrating membrane 9. Similarly, the upper outflow port 39 and the lower outflow port 59 are also provided on the side surfaces of the upper member 3 and the lower member 5 in the same direction, that is, the side surfaces on the right-hand side, respectively. However, since the upper outflow port 39 and the lower outflow port 59 deviate from each other in the lateral direction, the upper outflow port 39 and the lower outflow port 59 are disposed at positions where they do not overlap with each other in the film thickness direction of the vibrating membrane 9.

When the upper inflow port 37 and the lower inflow port 57 are disposed at positions where they overlap with each other, spaces above and below the vibrating membrane 9 become empty spaces. Thus, when the vibrating membrane 9 vibrates, a stress strain causes an opening area of each inflow port to change according to the vibration. In addition, durability of the vibrating membrane 9 is also lowered. Therefore, by displacing the upper inflow port 37 and the lower inflow port 57 in the lateral direction so that they do not overlap with each other in the vertical direction, the opening area of each inflow port is prevented from fluctuating, and the durability of the vibrating membrane 9 is also improved. Similarly, by disposing the upper outflow port 39 and the lower outflow port 59 at positions where they do not overlap with each other, the opening area of each outflow port is prevented from fluctuating, and the durability of the vibrating membrane 9 is improved.

In addition, as shown in FIG. 1 , the upper outflow path 35 and the lower outflow path 55 are disposed at positions where at least portions of them overlap with each other in the film thickness direction of the vibrating membrane 9, and merge into a single path at this overlapping position. As a result, when these paths 35 and 55 merge into the single path, since a fluid flowing out from one path attracts a fluid that flows out next from the other path, an outflow efficiency of the fluid can be improved by an inertial force.

Operation of Micro Pump

Next, an operation of the micro pump 1 according to the present embodiment will be described. The micro pump 1 according to the present embodiment applies the driving voltages from the electrode pads 60 to the piezoelectric element 11 to displace the vibrating membrane 9 in the vertical direction and to flow the fluid in and out with respect to the outside by the vertical movement.

Specifically, as shown in FIG. 5 , when the vibrating membrane 9 is displaced toward the upper space 31, the fluid flows out from the upper space 31 to the outside and flows into the lower space 51 from the outside, as indicated by arrows. That is, when the vibrating membrane 9 is displaced upward, since a volume of the upper space 31 decreases, the fluid flows out from the upper space 31 to the outside via the upper outflow path 35. At this time, since a shape of the upper inflow path 33 when viewed from the film thickness direction of the vibrating membrane 9 is such that the width of the upper inflow path 33 gradually widens from the outside toward the upper inflow port 37, the fluid is prevented from flowing back from the upper space 31 to the outside even without a check valve.

In addition, when the vibrating membrane 9 is displaced upward, since a volume of the lower space 51 increases at the same time, the fluid flows into the lower space 51 from the outside via the lower inflow path 53. At this time, since the shape of the lower outflow path 55 when viewed from the film thickness direction of the vibrating membrane 9 is such that the width of the lower outflow path 55 gradually widens from the lower outflow port 59 toward the outside, the fluid is prevented from flowing back from the outside to the lower space 51 even without a check valve.

On the other hand, as shown in FIG. 6 , when the vibrating membrane 9 is displaced toward the lower space 51, the fluid flows out from the lower space 51 to the outside and flows into the upper space 31 from the outside, as indicated by arrows. That is, when the vibrating membrane 9 is displaced downward, since the volume of the lower space 51 decreases, the fluid flows out from the lower space 51 to the outside via the lower outflow path 55. At this time, since that shape of the lower inflow path 53 when viewed from the film thickness direction of the vibrating membrane 9 is such that the width of the lower inflow path 53 gradually widens from the outside toward the lower inflow port 57, the fluid is prevented from flowing back from the lower space 51 to the outside even without a check valve.

In addition, when the vibrating membrane 9 is displaced downward, since the volume of the upper space 31 increases at the same time, the fluid flows into the upper space 31 from the outside via the upper inflow path 33. At this time, since the shape of the upper outflow path 35 when viewed from the film thickness direction of the vibrating membrane 9 is such that the width of the upper outflow path 35 gradually widens from the upper outflow port 39 toward the outside, the fluid is prevented from flowing back from the outside to the upper space 31 even without a check valve.

As described above, the micro pump 1 according to the present embodiment causes the fluid to flow in and out with respect to the outside by moving the vibrating membrane 9 vertically.

Effects of First Embodiment

As described above in detail, the micro pump 1 according to the present embodiment displaces the vibrating membrane 9 toward the upper space 31 to cause the fluid to flow out from the upper space 31 to the outside and to flow in from the outside to the lower space 51. On the other hand, the micro pump 1 according to the present embodiment displaces the vibrating membrane 9 toward the lower space 51 to cause the fluid to flow out from the lower space 51 to the outside and to flow in from the outside to the upper space 31. As a result, since the fluid can flow out both when the vibrating membrane 9 is displaced upward and when the vibrating membrane 9 is displaced downward, a flow rate can be increased even when the micro pump 1 is small in size.

In particular, the conventional micro pumps have a structure in which a fluid flows out to the outside only when a vibrating membrane is displaced upward or only when the vibrating membrane is displaced downward. However, in the micro pump 1 according to the present embodiment, the fluid can flow out from the upper space 31 when the vibrating membrane 9 is displaced upward, and the fluid can flow out from the lower space 51 when the vibrating membrane 9 is displaced downward. Therefore, since the fluid can flow out both when the vibrating membrane 9 is displaced upward and when the vibrating membrane 9 is displaced downward, a flow rate double that of the conventional micro pumps in comparison can flow out.

In addition, in the micro pump 1 according to the present embodiment, the upper inflow port 37 and the lower inflow port 57 are disposed at positions where they do not overlap with each other in the film thickness direction of the vibrating membrane 9. Thus, it is possible to prevent the inflow ports from being disposed to overlap with each other in the vertical direction and prevent the spaces above and below the vibrating membrane 9 from becoming empty spaces. Therefore, even when the vibrating membrane 9 vibrates, it is possible to prevent the opening area of each inflow port from fluctuating due to a stress strain, thereby improving the durability of the vibrating membrane 9.

In addition, in the micro pump 1 according to the present embodiment, the shape of the upper inflow path 33 when viewed from the film thickness direction of the vibrating membrane 9 is such that the width of the upper inflow path 33 gradually widens from the outside toward the upper inflow port 37. As a result, it is possible to prevent the fluid from flowing back from the upper space 31 to the outside even without a check valve. In addition, the shape of the lower inflow path 53 when viewed from the film thickness direction of the vibrating membrane 9 is such that the width of the lower inflow path 53 gradually widens from the outside toward the lower inflow port 57. As a result, it is possible to prevent the fluid from flowing back from the lower space 51 to the outside even without a check valve.

In addition, in the micro pump 1 according to the present embodiment, the upper outflow port 39 and the lower outflow port 59 are disposed at positions where they do not overlap with each other in the film thickness direction of the vibrating membrane 9. Thus, it is possible to prevent the outflow ports from being disposed to overlap with each other in the vertical direction and prevent the spaces above and below the vibrating membrane 9 from becoming empty spaces. Therefore, even when the vibrating membrane 9 vibrates, it is possible to prevent the opening area of each outflow port from fluctuating due to a stress strain, thereby improving the durability of the vibrating membrane 9.

In addition, in the micro pump 1 according to the present embodiment, the upper outflow path 35 and the lower outflow path 55 are disposed at positions where at least portions of them overlap with each other in the film thickness direction of the vibrating membrane 9 and merge into a single path at this overlapping position. As a result, when merging into the single path, since a fluid flowing out from one path attracts a fluid that flows out next from the other path, the outflow efficiency of the fluid can be improved by an inertial force.

In addition, in the micro pump 1 according to the present embodiment, the shape of the upper outflow path 35 when viewed from the film thickness direction of the vibrating membrane 9 is such that the width of the upper outflow path 35 gradually widens from the upper outflow port 39 toward the outside. As a result, it is possible to prevent the fluid from flowing back from the outside to the upper space 31 even without a check valve. In addition, the shape of the lower outflow path 55 when viewed from the film thickness direction of the vibrating membrane 9 is such that the width of the lower outflow path 55 gradually widens from the lower outflow port 59 toward the outside. As a result, it is possible to prevent the fluid from flowing back from the outside to the lower space 51 even without a check valve.

In addition, in the micro pump 1 according to the present embodiment, the vibrating membrane 9 is formed in the lower member 5 in which the lower space 51 is formed, the shapes of the upper space 31 and the lower space 51 when viewed from the film thickness direction of the vibrating membrane 9 is circular, and the diameter of the lower space 51 is smaller than the diameter of the upper space 31. As a result, since the outer periphery of the vibrating membrane 9 is disposed inside the inner peripheral surface of the upper space 31, the influence of the vibration of the vibrating membrane 9 on the upper member 3 can be reduced, thereby improving the durability.

Second Embodiment

Next, a micro pump 1 according to a second embodiment will be described with reference to FIGS. 7 and 8 . The micro pump 1 according to the present embodiment is different from the first embodiment in that inflow paths and outflow paths are disposed on non-opposite side surfaces of a quadrangular member. Hereinafter, descriptions of contents that overlap with the first embodiment will be omitted, and differences will be mainly described below.

In the first embodiment, as shown in FIG. 3 , since the upper inflow path 33 and the upper outflow path 35 are disposed on the opposite side surfaces of the upper member 3, the upper inflow path 33 and the upper outflow path 35 are arranged side by side in a straight line. Therefore, a strong stress may be applied on the straight line where the upper inflow path 33 and the upper outflow path 35 are aligned. Similarly, in the lower member 5 shown in FIG. 4 , a strong stress may be applied on a straight line where the lower inflow path 53 and the lower outflow path 55 are aligned.

On the other hand, in the micro pump 1 according to the present embodiment, as shown in FIG. 7 , the upper inflow path 33 and the upper outflow path 35 are arranged on non-opposite side surfaces of the upper member 3. Similarly, as shown in FIG. 8 , the lower inflow path 53 and the lower outflow path 55 are arranged on non-opposite side surfaces of the lower member 5.

As a result, since the upper inflow path 33 and the upper outflow path 35 are not arranged side by side in a straight line, it is possible to prevent application of a strong stress, thereby ensuring strengths during manufacturing. In addition, it is possible to make the strength in the vertical direction and the strength in the horizontal direction of the upper member 3 equal to each other. Similarly, in the lower member 5 as well, since the lower inflow path 53 and the lower outflow path 55 are not arranged side by side in a straight line, it is possible to prevent application of a strong stress, thereby ensuring strengths during manufacturing. In addition, it is possible to make the strength in the vertical direction and the strength in the horizontal direction of the lower member 5 equal to each other.

Modification

In FIGS. 7 and 8 , the upper outflow path 35 and the lower outflow path 55 are disposed on different side surfaces, but as shown in FIG. 9 , the lower member 5 may be rotated by 90 degrees with the normal direction at a center of the vibrating membrane 9 as a central axis so that the upper outflow path 35 and the lower outflow path 55 are disposed on the same side surface. Further, the upper outflow path 35 and the lower outflow path 55 are disposed at positions where at least portions of them overlap with each other in the film thickness direction of the vibrating membrane 9, and the opening 65 is provided at this overlapping position to merge the upper outflow path 35 and the lower outflow path 55 into a single path. As a result, when merging into the single path, since a fluid flowing out from one path attracts a fluid that flows out next from the other path, the outflow efficiency of the fluid can be improved by an inertial force. In addition, even in this case, since the upper outflow port 39 and the lower outflow port 59 are disposed at positions where they do not overlap with each other in the vertical direction, even when the vibrating membrane 9 vibrates, it is possible to prevent the opening area of each outflow port from fluctuating due to a stress strain, thereby improving the durability of the vibrating membrane 9.

Effects of Second Embodiment

As described above in detail, in the micro pump 1 according to the present embodiment, the upper member 3 and the lower member 5 each have a quadrangular shape when viewed from the film thickness direction of the vibrating membrane 9, and the upper inflow path 33 and the upper outflow path 35 are disposed on the non-opposite side surfaces of the upper member 3. In addition, the lower inflow path 53 and the lower outflow path 55 are disposed on the non-opposite side surfaces of the lower member 5. As a result, since the inflow path and the outflow path are not arranged side by side in a straight line, it is possible to prevent application of a strong stress, thereby ensuring the strengths during manufacturing. In addition, it is possible to make the strength in the vertical direction and the strength in the horizontal direction of the upper member 3 and the lower member 5 equal to each other.

In addition, in the micro pump 1 according to the present embodiment, the upper outflow path 35 and the lower outflow path 55 are disposed at positions where at least portions of them overlap with each other in the film thickness direction of the vibrating membrane 9 and merge into a single path at this overlapping position. As a result, when merging into the single path, since a fluid flowing out from one path attracts a fluid that flows out next from the other path, the outflow efficiency of the fluid can be improved by an inertial force.

It should be noted that the above-described embodiments are examples of the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and even in forms other than the above-described embodiments, it goes without saying that various modifications can be made in accordance with a design and the like without departing from the technical ideas of the present disclosure.

Supplementary Notes Supplementary Note 1

A micro pump including: a vibrating membrane on which a piezoelectric element is stacked; an upper space provided in contact with an upper surface of the vibrating membrane; and a lower space provided in contact with a lower surface of the vibrating membrane, wherein by displacing the vibrating membrane toward the upper space, a fluid flows out from the upper space to an outside and flows in from the outside to the lower space, and wherein by displacing the vibrating membrane toward the lower space portion, the fluid flows out from the lower space to the outside and flows in from the outside to the upper space.

Supplementary Note 2

The micro pump of Supplementary Note 1, wherein an upper inflow port, which is provided on a side surface of the upper space and configured to allow the fluid to flow in from the outside to the upper space, and a lower inflow port, which is provided on a side of the lower space and configured to allow the fluid to flow in from the outside to the lower space, are disposed at positions where the upper inflow port and the lower inflow port do not overlap with each other in a film thickness direction of the vibrating membrane.

Supplementary Note 3

The micro pump of Supplementary Note 2, wherein an upper inflow path connecting the upper inflow port and the outside has a shape in which the upper inflow path gradually widens from the outside toward the upper inflow port, when viewed from the film thickness direction of the vibrating membrane, and wherein a lower inflow path connecting the lower inflow port and the outside has a shape in which the lower inflow path gradually widens from the outside toward the lower inflow port, when viewed from the film thickness direction of the vibrating membrane.

Supplementary Note 4

The micro pump of any one of Supplementary Notes 1 to 3, wherein an upper outflow port, which is provided on a side surface of the upper space and configured to allow the fluid to flow out from the upper space to the outside, and a lower outflow port, which is provided on a side surface of the lower space and configured to allow the fluid to flow out from the lower space to the outside, are disposed at positions where the upper outflow port and the lower outflow port do not overlap with each other in a film thickness direction of the vibrating membrane.

Supplementary Note 5

The micro pump of Supplementary Note 4, wherein an upper outflow path connecting the upper outflow port and the outside and a lower outflow path connecting the lower outflow port and the outside are disposed at positions where at least portions of the upper outflow path and the lower outflow path overlap with each other in the film thickness direction of the vibrating membrane, and merge into a single path at the overlapping position.

Supplementary Note 6

The micro pump of Supplementary Note 4 or 5, wherein an upper inflow path connecting the upper outflow port and the outside has a shaped in which the upper outflow path gradually widens from the upper outflow port toward the outside, when viewed from the film thickness direction of the vibrating membrane, and wherein a lower outflow path connecting the lower outflow port and the outside has a shape in which the lower outflow path gradually widens from the lower outflow port toward the outside, when viewed from the film thickness direction of the vibrating membrane.

Supplementary Note 7

The micro pump of any one of Supplementary Notes 1 to 6, wherein the vibrating membrane is formed on a lower member in which the lower space is formed, wherein the upper space and the lower space have a circular shape when viewed from a film thickness direction of the vibrating membrane, and wherein a diameter of the lower space is smaller than a diameter of the upper space.

Supplementary Note 8

The micro pump of any one of Supplementary Notes 1 to 7, wherein each of an upper member in which the upper space is formed and a lower member in which the lower space is formed has a quadrangular shape when viewed from a film thickness direction of the vibrating membrane, wherein an upper inflow path configured to inflow the fluid from the outside into the upper space and an upper outflow path configured to outflow the fluid from the upper space to the outside are disposed on non-opposite side surfaces of the upper member, and wherein a lower inflow path configured to inflow the fluid from the outside into the lower space and a lower outflow path configured to outflow the fluid from the lower space to the outside are disposed on non-opposite side surfaces of the lower member.

According to the present disclosure in some embodiments, it is possible to provide a micro pump capable of increasing a flow rate even when the micro pump is small in size.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures. 

What is claimed is:
 1. A micro pump comprising: a vibrating membrane on which a piezoelectric element is stacked; an upper space provided in contact with an upper surface of the vibrating membrane; and a lower space provided in contact with a lower surface of the vibrating membrane, wherein by displacing the vibrating membrane toward the upper space, a fluid flows out from the upper space to an outside and flows in from the outside to the lower space, and wherein by displacing the vibrating membrane toward the lower space, the fluid flows out from the lower space to the outside and flows in from the outside to the upper space.
 2. The micro pump of claim 1, wherein an upper inflow port, which is provided on a side surface of the upper space and configured to allow the fluid to flow in from the outside to the upper space, and a lower inflow port, which is provided on a side of the lower space and configured to allow the fluid to flow in from the outside to the lower space, are disposed at positions where the upper inflow port and the lower inflow port do not overlap with each other in a film thickness direction of the vibrating membrane.
 3. The micro pump of claim 2, wherein an upper inflow path connecting the upper inflow port and the outside has a shape in which the upper inflow path gradually widens from the outside toward the upper inflow port, when viewed from the film thickness direction of the vibrating membrane, and wherein a lower inflow path connecting the lower inflow port and the outside has a shape in which the lower inflow path gradually widens from the outside toward the lower inflow port, when viewed from the film thickness direction of the vibrating membrane.
 4. The micro pump of claim 1, wherein an upper outflow port, which is provided on a side surface of the upper space and configured to allow the fluid to flow out from the upper space to the outside, and a lower outflow port, which is provided on a side surface of the lower space and configured to allow the fluid to flow out from the lower space to the outside, are disposed at positions where the upper outflow port and the lower outflow port do not overlap with each other in a film thickness direction of the vibrating membrane.
 5. The micro pump of claim 4, wherein an upper outflow path connecting the upper outflow port and the outside and a lower outflow path connecting the lower outflow port and the outside are disposed at positions where at least portions of the upper outflow path and the lower outflow path overlap with each other in the film thickness direction of the vibrating membrane, and merge into a single path at the overlapping position.
 6. The micro pump of claim 4, wherein an upper inflow path connecting the upper outflow port and the outside has a shape in which the upper outflow path gradually widens from the upper outflow port toward the outside, when viewed from the film thickness direction of the vibrating membrane, and wherein a lower outflow path connecting the lower outflow port and the outside has a shape in which the lower outflow path gradually widens from the lower outflow port toward the outside, when viewed from the film thickness direction of the vibrating membrane.
 7. The micro pump of claim 1, wherein the vibrating membrane is formed on a lower member in which the lower space is formed, wherein the upper space and the lower space have a circular shape when viewed from a film thickness direction of the vibrating membrane, and wherein a diameter of the lower space is smaller than a diameter of the upper space.
 8. The micro pump of claim 1, wherein each of an upper member in which the upper space is formed and a lower member in which the lower space is formed has a quadrangular shape when viewed from a film thickness direction of the vibrating membrane, wherein an upper inflow path configured to inflow the fluid from the outside into the upper space and an upper outflow path configured to outflow the fluid from the upper space to the outside are disposed on non-opposite side surfaces of the upper member, and wherein a lower inflow path configured to inflow the fluid from the outside into the lower space and a lower outflow path configured to outflow the fluid from the lower space to the outside are disposed on non-opposite side surfaces of the lower member. 